Heavy Metal: the Science of Cast Iron Cooking

I originally wrote this piece for a print publication, but they said the tone was too dry and axed it. They said they wanted something more like the blog. Here it is on the blog.

Heavy Metal

Cast Iron Intro:

While cast-iron cookware has been available for centuries, the advent of industrialized factory production in the mid 1800’s allowed cast iron to become widely available. The cast-iron skillet quickly became an icon of American cooking. Cast iron could be cheaply produced with minimum tooling in a wide variety of shapes –waffle irons, corn-shaped muffin pans, dutch ovens (dutch meaning “fake”, not “from Holland”), and skillets of every size. While many of these manufacturing advantages have since been supplanted, cast iron’s characteristic properties make it an excellent cookware choice in the modern kitchen. Corn bread made the classic way, in a pre-heated cast iron skillet, highlights cast iron’s cooking advantages: its temperature delivery power generates a good crust, and its temperature-regulating power provides even, constant heat –leveling out the temperature variations of your oven. The science of cast iron shows how these advantages work.

Cast Iron as a Pan Material:

The popular wisdom that cast iron cookware provides even heat is misleading. A cast iron skillet placed on a gas burner will develop distinct hot spots where the flame touches the pan. If you heat the center of a cast iron pan you will find that the heat travels slowly towards the pan’s edge, with a significant temperature gradient between the center and the edge. The pan will heat very unevenly, because cast iron is a relatively poor heat conductor compared to materials like aluminum and copper. An aluminum pan will heat more evenly because heat travels quickly across aluminum. Because of poor heat conduction, undersized burners are incompatible with cast iron cooking. The edges of a large cast iron pan will never get hot on a tiny burner. On properly sized burners you can minimize hot spots by heating slowly, but the best way to evenly heat cast iron is in the oven.

Sprinkling flour onto pans allows us to check their heating patterns. Just sprinkle with flour and heat. This is a variation on the technique Harold McGee uses. He puts paper in the bottom of a pan, covers the paper with beans, turns on the heat and makes a permanent print of the pan's heating pattern.

A flour-dusted cast-iron pan being heated on a high output burner. Notice the intensity of the hot spot and how uneven the browning is.

The mainly aluminum All-Clad has a much more even heat pattern on the same burner.

The cast-iron pan also shows some serious un-evenness on our induction burner.

The aluminum is more even than the cast-iron, but still not great. The induction burner's element is too small. Even a good conductor can't make up for a burner that is too small.

Cast iron has a higher heat capacity than copper, so it takes more energy to heat a pound of cast iron to a given temperature than a pound of copper. More energy is stored in each pound of the cast iron. Aluminum has a higher heat capacity than iron (it stores more heat per pound) but is much less dense than iron. For a given volume, therefore, cast iron stores more heat than aluminum. Because cast iron pans typically weigh much more and are thicker than the same size pan in another material, they tend to store more energy when heated. This combination of high heat capacity and weight means that cast iron takes a long time to get hot. Once hot, however, a cast iron pan usually contains more thermal energy than other pans at the same temperature — a significant cooking advantage. Cast iron has unparalleled searing power because it has a lot of available thermal energy – and unlike almost any other type of pan, cast iron pans won’t warp when left dry on a burner to heat up. Thick and heavy cast iron will remain flat and true.

Cast iron is slow to heat up, so it’s also slow to cool down. It is a good regulator. It retains its temperature longer than other materials and won’t produce temperature spikes. This behavior can be disconcerting to the uninitiated. Cooking with cast iron is more akin to driving a boat than a car: the pan doesn’t respond instantly to changes in the applied heat.

Cast Iron – the OG Non-Stick Material:

Cast iron is naturally non-stick when seasoned properly. New cast iron is anything but non-stick, and it can easily rust. Seasoning — rubbing oil or fat into the cast iron and subsequently heating it — fixes both problems. Unsaturated fats work best (unsaturated means that some of the carbons in the fatty acid chains contain reactive double bonds). Nineteenth century American cooks typically used lard because it was readily available and unsaturated enough to polymerize well, but almost any oil will work. When an unsaturated fat is heated to high temperatures, especially in the presence of a good catalyst like iron, it is broken down and oxidized, after which it polymerizes –joins into larger mega molecules the same way plastics do – and mixes with bits of carbon and other impurities. This tough, impermeable surface adheres to the pores and crevices in the cast iron as it is forming. The surface is non-stick because it is hydrophobic – it hates water. Water soluble proteins make foods stick to their pan; a hydrophobic surface prevents sticking. The bits of carbon in the seasoning may also act as an additional release agent.

Cast iron isn't the only cookware with a burnt-oil based non-stick surface. This is a Korean dolsot --hot stone bowl. I routinely heat this thing to 615 F. I love dolsots. I have 8. I did not say anything about them in this post, but I could not resist putting in a picture. Maybe I'll do a post.

There is no quick way to fully season a cast iron pan; the surface of cast iron becomes slicker and blacker the more it is used. Though most cast iron today is sold “pre-seasoned,” this cursory seasoning protects against rust, but not against sticking. A good non-stick surface forms over time, with use. The oil polymer on a well-used piece of cast iron is built of many thin layers deposited over time. Thick layers can flake off in large pieces. Thin layers will remain adhered to the pan and will slough off microscopically. A true seasoned surface will only form properly at temperatures well in excess of the 350-375 degree F temperature that some manufacturers recommend for seasoning cast iron. Low temperatures do not completely polymerize and break down oil and will leave a brown, somewhat sticky pan instead of a black, non-stick one. 400-500 degrees F is the effective range for seasoning.

Good seasoning is good protection. Both these pans received the same amount of abuse and neglect. The one on the left was newly seasoned, the one on the right is 50 years old.

Early cast iron was sold either polished or unpolished. Polished cast iron isn’t polished the way silver is, it merely has a surface that was sanded or machined to make it smoother. The polishing process reveals more of the internal pore structure of the iron, and these pores make the seasoning adhere better to the pan. Polished cast iron is slick like glass when properly seasoned. Most modern cast iron is unpolished, meaning its surface has a pebbly appearance from the grain of the mold in which it was cast. Eventually, through years of seasoning, unpolished cast iron can become extremely smooth, but never as smooth as polished cast iron. New, unpolished pans can be sanded with rough sandpaper to approximate polishing.

The bumpy, non-polished surface on the left is now standard for cast iron, older pans also came polished, like the one on the right --a much better surface.

Caring For Cast Iron:

Many cooks are unnecessarily worried about maintaining their cast iron cookware. The seasoning on a good piece of cast iron is very durable. Modern soap will not harm seasoned cast iron. Old, lye based cleaners will hurt seasoned cast iron because lye dissolves the oil-polymer. Seasoned cast iron can also tolerate gentle scrubbing with non-metallic abrasives. Vigorous washing is not recommended on new, weakly seasoned pans.

Sometimes, the surface of a cast iron pan can become damaged through abuse or neglect. In this case the pan has to be stripped down to metal and re-seasoned. The best way to remove an old or bad seasoning job is to use a fireplace or the self-clean cycle of your oven to reduce the seasoning layer to ashes. This happens around 800 degrees F.

Another good maintenance technique with cast iron is to use metal cooking implements. The gentle scraping of metal along the bottom of the pan while cooking helps to even out the surface of the seasoning and make it more durable, not less.

Cast Iron Nutrition:

Studies show that cooking in cast iron can leach iron into food. Foods that are high in moisture, very acidic, or are long-cooked leach the most. For many people the extra iron is beneficial, but for a small minority of people who are sensitive to iron it can be harmful. The most quoted study on the effects of cast iron cookware on iron levels is the July 1986 study in the Journal of the American Dietetic Association. The pan used in that study had only been seasoned by daily usage for a couple of weeks prior to the study. As the study pointed out, better seasoned pans leach less iron. There are no data on iron leaching in decades-old pans.

You can find them on eBay for less than new Lodge pans for most common sizes (7-8-9-10). They are burnished (machined) so they are smooth, and the iron is of such quality that they are thinner, lighter, but stronger than the Lodge equivalents.

I got most of my skillets for $10-15 plus shipping. Like everything on ebay, be patient and look at the pictures closely to make sure you are getting a pan that has not been abused.

Very insightful. I feel a bit like an idiot since I have recommended cast iron pans, because they have the best even heat. Wrong!

I could have known. Grilling green asparagus on my cast iron grilling pan is by far my favourite technique of cooking the stalks, but it always seemed (and in fact was the case after reading your post) the asparagus placed directly above the burners got grill marks much faster than the ones on the periphery of the pan, even after a pre heating process. I’m getting better at resisting long standing kitchen claims, but still not there.

Dave, so the best way to improve my grill pan is to season it (I don’t use it that often for a natural seasoning over time) and then polish it?

Howdy Auldo,
The polishing would happen before the seasoning. If you sand it after it is seasoned you will wipe out the seasoning and have to start over. On grill pans I don’t think the polishing will help much because it has those ridges anyway. Another thing about grill pans –unlike other pans they are expected to get really-really-really hot. If it gets super-duper hot (I would guess over 700 F or so) you’ll start burning off the seasoning. I have seen it happen. It doesn’t hurt the pan any.

Thanks Dave,
I am a regular user of cast iron, somewhat of a collector, and a metallurgical engineer and, as such, I feel qualified to comment. I find your article to be quite accurate and, as usual, well done.

I have a particular fondness for Martin cast iron. Since the company has been out of the cast iron cookware business for many decades, it is only available in flea markets or usually on eBay.

The polish on the Martin is the best that I have seen and it responds well to good seasoning technique. For reference, the full name is Martin Stove and Range Company, Florence Alabama. For the cast iron geek/collector, the Martins have some distinctive design elements and an ornate label cast into the bottom.

For a really deep restoration on some of the really nasty pieces that I have acquired I have preheated the piece in the oven to around 450F and then transfered quickly to a high-power, propane ‘Cajun’ burner outside and heated the piece all the way to a dull red heat. The preheat is needed to avoid thermal shock and cracking, yes it can, trust me! This will take the piece back to the condition that it was in the day it was born – ready for re-seasoning and use.

For re-seasoning I have come to prefer a hydrogenated fat such as Crisco.

I regularly use my Grandmothers skillets that she acquired as a young girl. She was born in 1898. These appear to be more durable than grandmother, my mother and in a few years will prove to be more durable than me.

The top quality older pieces such as Martin, Wagner, Griswold and Vollrath are worth seeking out since they are usually far superior to the modern product.

Lodge cast iron is the modern product that is generally available from a number of sources. I am sure that it has some uses but not for me.

Always use the burner that matches the bottom of the cooking pan. The above examples showed large pans on small burners, thus the burn patterns.

Indeed, the older cast iron pans, General Housewares who are no longer producing, offered a very smooth finish. Lodge Manf, the sole remaining US maker of cast iron cookware, offers a rough finish, which I personally do not favor.

The versatility of cast iron is unquestionable, whether on top of the stove or in it. You can have all your Clad cookware paying 300 dollars for a single pan. Ridiculous.

This is one of the most thorough articles on cast iron I’ve ever read. Thank you for debunking so much of the myth that lingers out there! I cooked some tomatoes in a cast iron dutch oven (d’oh!) and I thought that I had to reason my entire pot a la crisco + 1hr @ 350F. The seasoning seemed to have taken, but the smell was horrendous! Do you have any suggestion for avoiding this reseasoning or cutting down on the smell? (Is it the crisco? Is the iron?). Thank you!

Hello Ceda,
Cooking acidic food in your cast iron won’t necessarily ruin it. I have cooked many a tomato in my old cast iron. Acidic ingredients tend to casue more iron leaching than non acidic foods. I would also guess that acid foods could cause some rusting in a newly seasoned pan (plus it will taste bad). If your pan isn’t rusted you don’t need to season from scratch. Adding additional seasoning can’t hurt, however. It will smoke like a bastard.

Hi Adam,
Sanding will definitely remove the seasoning. Acid usually won’t, but may promote rusting on a newly seasoned pan. Lye, or very alkaline detergents, on the other hand, are quite effective seasoning destroyers, which is why oven cleaner can be used to strip seasoning. For a new seasoning I would definitely repeat the oil and heat procedure a couple of times. The most fun I ever had seasoning a piece of iron was my crepe maker. I have a full on gas powered Krampouz crepe maker. That guy is seasoned by firing up the burner and repeatedly wiping oil into the surface. I use that thing constantly.

Thanks for this great post! Very informative. I’d love to see a whole post on best seasoning methods–there’s sure a whole lot here but I’d love even more in-depth how-to. That’s my number one question regarding cast iron.

Do you have any citations for the polymerization of the fatty acids to form a seasoned surface? I’ve seen the same statement in McGee’s On Food and Cooking but when I contacted him he was unable to point me to any scholarly articles relating to the topic.

I must confess I’m skeptical of the “oil polymer” concept, believing it to be Fe3O4 with an oil surface. And the “porosity” of cast iron is dubious; as far as I know metals are rarely porous when cast from liquid melted metal. But having said all that, I cook with cast iron much of the time; it’s great.

I have never successfully seasoned an iron skillet (in my life, about 5) without smoking up the kitchen. I suggest 380 F.

Howdy Jumper,
We are on opposite sides of the fence. I’m skeptical about the black iron oxide. The conditions in the pan aren’t similar to the conditions in a gun blueing tank (no caustics, etc). Another reason i am skeptical is that high heat removes the seasoning without leaving the pan with a protective black oxide coating (it will easily rust). Many cast metals are quite pourous if they aren’t cast well, however, most good cast iron seems to be “free of porosity” as the literature says. All of the non-ductile cast irons, however, have large flakes of pure graphite in them, which add lubricity, but are quite soft. I imagine that they could act like a porous surface after they have been degraded. I leave the question to our commentors.

That would explain why my old cast iron frypan is so smooth, I’ve always wondered. I have no idea how old it is, but it was ancient when I acquired it around 1974.

What do you think about non-cast iron? I have a couple of frypans that are made from “black iron” which is just spun sheet steel I think. It seasons exactly the same as cast iron, but is a good deal lighter. Much easier for me to pick up one-handed when full of stuff.

I love those steel pans! I have one that’s quite thin (thicker than a wok, but still pretty light) and one that’s about 2+mm thick, so it’s medium-heavy. They have a cast iron-like finish but are very responsive (the thin one particularly). They’re a joy to cook with. Though I suppose part of the reason I like them is that they look all gnarly and restauranty and I’m kind of a lame poseur that way.

Wagner (now American Culinary(?)) has or used to have polished cast-iron. I was going to get some a few years ago, but then I thought they went out of business or something, so I never did. According to this link, though, they seem to still be around:

Yep. They start off being sort of silvery but turn completely black after use the same way cast iron does, and the surface is exactly the same. I got mine from the place that makes them which is not far from where I work, but they stock them in all the restaurant supply places. They tend not to be available in ordinary kitchen shops, possibly because they’re not very beautiful. They do come in very large sizes – I have one that’s about 40cm in diameter (the biggest I can use on my stove, but far from the biggest available) that I use on a wok burner turned down low. It’s great for cooking breakfast for a crowd.

I would say cast iron just simply for the seasoning aspect. Think of all the times you hear people refer to good ol’ southern food. That kind of food is usually cooked in a cast iron pan or pot. I can remember growing up my grandmothers both always used cast iron. I have never seen any of my family use copper, but I cant see how it would give the same flavor as cast iron.

Is there any more information on the nature of the seasoned surface that develops?

– It’s “naturally non-stick” but I’ve never seen a cast-iron surface, even a very long-seasoned one, that can begin to compete with Teflon for ungreased release. Is there a scale for measuring nonstickiness?

– The polymer tends to retain flavors a bit, no? Even after a good soapy cleaning there’s the risk of garlicky pancakes in the morning. Any way to mitigate that?

Paul A., Teflon is tempting because of the non-stick factor you mentioned, but more research is emerging about how dangerous it is even if it never gets scratched.

After years of being a Teflon junkie (but otherwise healthful living), I was diagnosed with cancer (only in my late 30’s). I started researching PFOA’s and other toxins released by Teflon at normal cooking temperatures and it prompted me to give away all my beloved Teflon (and I feel guilty that someone else will be exposing themselves to these toxins).

Sure, I miss being able to flip an omelet handily without a spatula, but the non-stick convenience is NOT worth the health risk. Hence my return to cast iron (which, over time, will be plenty “less-stick” for me) and stainless steel.

For non-stick I recently picked up a titanium-coated frying pan. The metal is inert and has none of the cancer dangers of teflon. I was dubious at first, but it has quickly become my favourite piece of cookware. A thick cast-aluminium body is coated all over by titanium (except for the flat bottom) and cleanup is as easy as wiping the surface with a paper towel. The thickness makes for good heat distribution and a pleasing heft in the hand. The one I bought was expensive, made in Germany, sold only at tradeshows or online, and in Canada is called by the suspiciously-generic name Titanium Exclusive. http://titaniumexclusive.com/

Now that I’ve found out how well it works, I’m on the search for a more affordable line.

That doesn’t mean I’d give up my cast iron! I use both, each as appropriate. I bought my cast iron set the first month after graduating college, which means they’re -mumblemumble- decades old now and still going strong.

Any thoughts on the use of heat diffusers? I use one when using large pots on my burners, particularly when doing a long simmer to avoid scorching. Do they really help? Or perhaps I should try your flour test, with and without.

Thanks for this great post. I’ve been considering a cast iron skillet for a while now and am curious about bare cast iron vs. enameled. I have an enameled dutch oven and love it. Risk of chipping aside, is an enameled skillet functionally equivalent to a bare one?

I have a question about cleaning. I tend to use salt as a scrubbing agent (baking soda if it’s not too yicky), hot water and no soap. When I am done scrubbing out the “big chunks” and the pan is still warm from the water, I dry it with a paper towel and wipe a bit of oil over the cooking surface. It seems to be working fairly well but there are still some things – most notably eggs when don’t pay attention to the heat – that still stick.

Is this because of the way I am cleaning? Should I be doing more? Less?

Hey Dave, I didn’t feel like going through 40 long posts to see if this was asked already. Doesn’t the induction burner naturally have a great tendency to have a concentrated hotspot as opposed to a high flame that conceivably covers more area with more heat? have you tried this with a real burner?

Hey Tom,
It depends on the configuration of the induction burner. Two of those pictures were on the schools high output gas burners and two were on the induction. There is no reason you couldn’t make an induction burner with a better pattern.

Great post on cast iron. I love using my skillet but I like my Cantonese wok more. It’s steel, not iron, but because it came with a smoother surface to begin with it is easier to season properly and keep ultra slick. Cooking with a skillet vs a wok couldn’t be more different though.

Anyway, the reason I’m commenting is to point out an error in your post. It takes more energy to heat a pound of aluminum than a pound of copper or a pound of iron. Aluminum has twice the specific heat of iron, .9 vs .45 joules per gram degree kelvin. When you compare the two pound for pound, aluminum takes twice as much energy to heat to a given temperature. However, cast iron is three times more dense than aluminum, 7.9 vs 2.7 grams per cubic centimeter, so you will never find an aluminum pan that is as heavy as a similarly sized cast iron skillet. Therefore, cast iron skillets will always have more heat capacity then their aluminum counterparts. If you could suck it up and deal with a half inch thick skillet, aluminum would make a far superior cooking implement pound for pound. Hard anodizing makes a comparable cooking surface to seasoned cast iron with less maintenance to boot. All that being said, I’ll still never trade in my cast iron for aluminum.

The wikipedia article on specific heat explains this more. Compare the “volumetric heat capacity” of various materials with their specific heat, which is measured per gram.

Dave P,
Thank you so much! I can’t believe no one caught that. I misread the specific heat tables when I was writing the article. I have changed it to reflect that iron has a higher specific heat than copper, but lower than aluminum, and that the significant density difference between aluminum and iron means that iron wins on a per-volume basis. Thanks again. I hate making errors.

I bought mine in 2 differnt places in Koreatown here in New York City. One is closed, the other is Han Ah Reum on 32nd Street between 5th and Broadway. You can also try http://www.hmart.com/. They don’t have it on their website, but someone at corporate said they might have them in their stores (you’d have to call the individual store locations). I have found that my pronunciation of the word Dolsot is so bad that Korean speakers can never ever understand what I’m asking for over the phone, so I always have to go in person to check.

I love this article that you wrote. Yes, it is often said that cast iron heats more evenly but what really occurs is that cast iron retains heat better than other materials. While it is ok on the stove top, it really shines where heat is applied not through conduction, like in an oven.

I’m not sure I believe that early pans were sanded, though I have not seen many early pans. Maybe. I do have an old to me, it was my Dad’s, cast iron griddle that appears to have a machined surface. I have been to the Lodge plant several times and know exactly how there pans are made. Their surface while not sanded, is not an as cast surface, it goes through several processes.

The difference between a sanded surface and a machined surface is significant. All cast iron has a skin that is 0.010-0.015″ deep. The skin is a complex surface made up of more than just iron because of the interaction with the sand mold. But because of dimensional variations, you normally have to remove 0.030″ before you are safely into a homogenous metal. I don’t think you can do that with sanding. Sanding will just make the surface smoother. However, if you were to machine off 0.030″ of material you would be exposing the Gray Iron. Gray Iron is the original metal matrix composite consisting of an iron matrix containing graphite flakes. A sometimes beneficial event occurs though when Gray Iron is machined in that the machine tool rips out some of those graphite flakes leaving behind microscopic pockets that allow for better adhesion of things like oil, or paint, and possibly in this case the polymerized seasoning.

Personally, when I have the money, I will probably switch to Olvida. I have had a lengthy discussion with the owner and am impressed with their products. The fact that their pans are NSF certified means a great deal to me, especially the ability to be run through a dish washer, which you can’t do with seasoned cast iron. Something to think about next time you are out eating fajitas. I believe that the trade off between the nickel coating versus the seasoning is negligible.

One thing that I think needs to be researched is the leaching of lead out of a cast iron pan and does the seasoning prevent it. We have strict restrictions on lead in US foundries. I’m not so sure about other countries.

By the way, how did you heat a non-magnetic aluminum pan on an induction top?

Howdy IanB,
Non ferrous metals will only heat due to I squared R losses, which isn’t usually enough to get pans hot with our current induction hobs (obviously it can be done because things like aluminum are smelted in induction furnaces every day). Ferrous materials also experience hysteresis loss, which is why they heat so much better.

I’d like to debunk another myth, which is the supposed “nonstick” characteristic of seasoned cast iron.

Seasoned cast iron could better be described as “less stick.” If our primary point of comparison is unseasoned stainless steel then, yes, seasoned cast iron is “less stick.” But it is nowhere near as nonstick as a PTFE-coated cooking surface. Try a comparison of cooking an egg with no added fat on a brand new PTFE-coated surface versus a seasoned cast iron surface, and the difference is quite obvious.

I have quite a bit of well seasoned 100+ year old Griswold I inherited, and wouldn’t describe any of it as “nonstick.”

To address questions about the best temperature for seasoning: it depends on the oil used. My understanding is that the seasoned surface is actually a mix of polymerized oil and carbonized oil (which explains both the blackness and the stick resistance … if you’ve ever had spots of brown polymerized oil on an aluminum or stainless pan, you’re probably aware that the stuff is about as sticky as it gets).

For new pans, I recommend getting a very refined, unsaturated oil that that lists the oil’s smoke point on the package. I’ve used safflower, grapeseed, or canola oil interchangeably. Set the oven to around 25 degrees F higher than this (I’ve arrived at this by guess, not science, but it seems to work).

Wipe a very thin, even coat of oil on the pan and pop in the oven for 20 or 30 minutes. Adjust the temperature if the oil doesn’t blacken, or if it seems to incinerate. You can pull it out and wipe on a new coat while the pan’s still hot. Repeat two or three times, and you’ll have a pan that looks like it’s been cooked on for years.

Love all things cooking. Having the right tools for each job is always important. Having food safe cookware that doesn’t impart its own flavor always helps too. I used to think stainless steel pans were too ‘sticky’ for most cooking until I saw this great article on Houseboat Eats titled “On properly heating your pan” (http://www.houseboateats.com/2009/12/on-properly-heating-your-pan.html). Now I’m curious if this technique works with cast iron…

Paul,
I believe you will find a temperature at which the leidenfrost effect (mentioned in that post) works with cast iron. I’m not sure that you really need to get it that hot though given the natural non-stick properties of well seasoned cast iron.

Dave, have you done actual comparisons of the searing power of cast iron and heavy copper? I’m suspecting the results would vary with the thermal mass of the food you’re searing. The iron pan will have somewhat more heat capacity, but the copper pan will be able to deliver the energy much more quickly to the food.

My hunch (untested) is that iron will do a more efficent job on a big chunk of meat, and copper will do better on a small one, at least on a low output range like what most of us have at home (which forces you to depend on stored energy). With lots of BTUs at your disposal, copper might have an edge even with a big portion.

Hey Paul R,
I dunno for certain. I can say this: When researching building the red-hot poker I had the occasion to heat up slugs of cast iron, stainless steel and copper and toss them into liquids to check their boiling power. The copper was, by far, the best. I think it was because the copper had a good amount of thermal energy and it was able to deliver that energy very quickly. The iron remained hotter longer but didn’t deliver as much of a whallop. The stainless was worthless.

This is partly because, in reality, most cast iron cookware does not have a significant advantage when it comes to thermal capacity. Sure, cast iron has a higher specific heat than copper (0.48 J/g/K versus 0.385). But copper has the edge in density (8.96 g/cm^3 versus 7.87). What this means is that the “specific heat per square centimeter” is not much higher for cast iron than it is for copper (3.53 J/cm^3/K versus 3.44).

Since cast iron pans are not, generally speaking, any thicker than a heavy gauge copper pan, they don’t have any real advantage when it comes to thermal capacity.

This means that a copper pan has around the same thermal capacity as a similarly-sized cast iron pan, but the copper pan can deliver the stored thermal energy much faster. That means better searing.

“This is partly because, in reality, most cast iron cookware does not have a significant advantage when it comes to thermal capacity.”

This had been my assumption, too, but then I weighed my copper pans and similar sized cast iron pans. I was surprised to find that in spite of copper’s higher density, the iron pans weighed significantly more. I calculated that the iron pans had as much as 60% more heat capacity. Some of this could be explained by differences in the pans’ shapes (the iron pans have higher sides … though the copper pans have longer handles). But I think the iron pans must just be significantly thicker than the 2.5mm copper. If I had calipers I’d check.

This is why I’m wondering if iron will have the advantage searing something big; the copper will deliver the energy fast, but just won’t have stored as much overall.

I think the best situation would be a copper pan on a burner with so many BTUs that you’re not dependent on stored heat. But that’s far from the case with my stove.

Hi, just a comment from the foundry side. It is extremely difficult to cast iron less than 3mm thick and for a Gray Iron pan the effort is probably not worth the cost. Under 3mm the iron is almost guaranteed to be carbidic meaning it will be a brittle as glass. Not good for a piece of cookware. Eyeballing my pans I think you will find the average cast iron pan (unmachined) to be on the order of 5mm thick.

Using a C-clamp and a bit of electrical tape (AKA the poor-man’s calipers) I measured my Lodge CI pan to be a bit thicker than 1/4 inch – right in line with your 5mm estimate, give or take a layer of seasoning.

If we do the math, we discover that the Griswold pan has a base of 642.4 cm^2 and another 511.9 cm^2 of material in the sides; whereas the Falk pan has a base of 452.4 cm^2 and another 557.9 cm^2 in the sides.

We know that the Falk is 2.5 mm thick, but having no calipers I don’t know the thickness of the Griswold pan. Since cast iron is… well, cast… it doesn’t need to have the same thickness throughout and I suspect that some may be thicker at the base than on the sides.

Anyway, so the Griswold skillet has 1154.3 cm^2 of material at some unknown thickness, and the Falk pan has 1010.3 cm^2 of material at 2.5 mm thickness.

Now I weighed them.

The Falk pan came to 2,260 grams, which is right around what we would expect. The Griswold pan came to 2,270 grams. Not all that different!

Now, my kitchen scale is not super accurate and I was measuring with a measuring tape, so these are approximations. But they’re pretty reasonable approximations for our purposes, and what they seem to show is that the Griswold pan is, if anything, a bit thinner than the Falk pan. If these two pans were exactly the same diameter, etc. we would expect the Falk pan to have greater thermal capacity.

Thickness is, I think, probably the best way to consider things like thermal capacity. If you have a thin pan that has a huge thermal capacity by virtue of having a very large diameter (or tall sides) it doesn’t help you much when you slap a steak down in the middle of the pan. There might be some small advantage for a material with very good thermal conductivity, but it’s not like all the thermal energy from 5 inches away is going to immediately flow into the steak. This is especially true with respect to materials that have lower thermal conductivity such as stainless steel, carbon steel and cast iron.

Hi Dave,
Great post, and very informative. I’m new to cast iron but and stuff I have is the French kind with an enamel coating. I’ve been told never to heat them above medium on the stovetop or 350 in the oven. One of the pieces I have is a roasting pan however and there are many things I like to cook that require higher temperatures. Do you know anything about this enamelled kind of CI? Whats the worst that can happen if I heat it to, say, 430?

I received a Le Creuset enameled Dutch oven as a gift a couple years ago. Mine also came with a similar warning, but it was about not putting the lid in an oven above 350 degrees because it has a plastic handle/knobby thing on top. I have seen metal replacements for this handle that are okay in the oven up to 450 degrees as well.

As far as the enamel in general, I have seared meat in it over high heat plenty of times with no ill effects at all.

This is just my experience of course, I can’t say yours will be the same (especially given that you didn’t mention the brand). Still, I would hope that most cookware of decent quality can handle heat above 350 degrees!

I’ve been to the Kohler plant several times and watched them enamel bathtubs. The curing temperature is well over 350°F. The Le Creuset Car & Use page states that the phenolic (plastic) knob is good to 375°F. I imagine that is the only limiting factor. I think a metal knob would be a great upgrade. I prefer Staub. My Staub does have a metal knob on the lid and their Care & Use page says the dishes are safe up to 500°F.

You mention you have Staub, which is supposed to not need curing before using. I bought the 10in. cast iron pan b/c I was curious about it. I’m having a hard time cooking eggs in it. They seem to stick, despite that I heat up the pan on low, for a longer period of time than I need to for my other pans. Do you have any suggestions?
Much appreciated. Christina

My wife rescued a le cruset dutch oven from the thrift store that had enamel pitting damage. I figured that even with the damage, I could use it for bread, since there’d be parchment in it.

* It’s fine in the oven @ 450. I ran it through a season cycle to treat the pits, and I’m preheating it there for the bread. No damage, no problem with the knob (yet).

* The enamel pits and pops out somewhere near the smoke point of canola on the stove. I had treated it something like how I do the a CI pan (after washing, wipe with oil and heat till just smoking), and it started pinging. The pinging was the enamel popping off the metal.

I’m guessing that it was at the thrift store cause someone turned the ring on below it for 10 minutes and came back very disappointed.

I’ve been using a creuset enameled dutch oven at very high heat e.g. 500F. To prevent damage, the first trick is to loosen the plastic knob slightly. The metal of the pot, the screw in the knob, and the plastic of the knob, all expand and contract at different rates. You’ll crack the knob unless you loosen it to allow for expansion under high heats. Normally you wouldn’t have to do this.

Secondly, if you’re planning for high heat, scrub the pot and lid thoroughly before you use it. Kitchen tools tend to pick up a film of dust and oil when stored for any period of time, and that stuff turns black when heated. Not a disaster, but it’s unsightly. It is far easier to clean that stuff off your pot before rather than after.

My white Creusets do discolor on their cooking surfaces though, when used at super heat. The interior turns a little brown. I’m not sure that can be prevented.

I just received a cast iron Dutch oven from Universal housewares products. It was made in Asia somewhere. Anyway, it has a lot of machine oil gobs in it. How do you recommend seasoning / cleaning this baby? Thanks.
Chef Barb Rolek

As mentioned, cast iron does not transfer heat readily-as in heating one spot does not transfer the heat to other spots. Its always a trade off between fast acting pans (aluminum/copper) vs slower (stainless) vs even slower (cast iron). Slower acting pans have the advantage of a very even overall temperature, irregardless of external conditions (gas fluctuation, air movement, or even taking off the lid).

In my opinion, the great overall evenness in temperature over the whole duration of cooking means more predictable results- flapjacks, pancakes, crepes, all turn out more consistent with cast iron over aluminum or stainless.

I polished mine with 150grit on a D/A sander, just to knock down the “high” spots. Then finished up with 400. Boil some water and use some scotch bright to make sure you open up the “pores” for the oil to stick.

I tried the crisco, the lard, the “fish fry”- all with marginal success. What I did like, and still use today, is pam. Get the pan hot out of the oven, with exhaust fan on, spray pam on it. then stick it back in. Do it a few times.

Then just start using it. Fried eggs and bacon for two weeks does wonders for the pan! Stay away from “liquidy” stuff (vegetables that create liquid and the like).

This is a great post, thanks to all. I’m a fan of the well-seasoned cast iron skillet but does anyone have much experience with the nickel-plated jobs? They’re a bit pricey. Is the finish smooth or pebbly? Do they develop a non-stick coating? And if not, what’s the point? And how long is the nickel coating expected to last? Any metallurgists out there know how well nickel bonds with iron? Will the coating be extant in 100 yrs time? Also, any comments on the black matte enamel pans out there? The instructions that came with my Creuset said it would season itself over time but that never happened. I just use it to make tarte tatin now. A good use…but not what I expected. Anyone have experience seasoning these pans? Is it true that if you use enamel cast iron over high heat the enamel breaks down? Thanks.

Now I used water filled pans with lids for the experiment – and this is of course very different from a skillet with regards to surface area etc., but still – I have an inkling that the “cast iron retains heat better” statement is more an assumption than a fact. I’d love to see you do some experiments here.

“In my opinion, the great overall evenness in temperature over the whole duration of cooking means more predictable results- flapjacks, pancakes, crepes, all turn out more consistent with cast iron over aluminum or stainless.”

Curious. My experience (and the science) argue against the opposite. Leaving aside pure stainless steel (which by any measure is a terrible thermal material for cookware), aluminum will work much better for pancakes than cast iron, provided it’s reasonably thick.

Crepes are probably a better test of this, since they cover the whole bottom of the pan. I have never been able to come close to an evenly browned crepe in any of my iron pans (on a gas flame). The pattern on the crepe shows the hot spots with perfect precision. Heavy aluminum and copper make very even crepes; light aluminum (all clad stainless) makes reasonably even ones.

These results are completely consistent with the physics of the materials.

Since I couldn´t find any polished cast iron in Germany I made a friend by some Wagner skillet and a large griddle plate for me (the poor fellow has to carry it over next time he flies to Europe since shipping is too expensive as well….)

BTW: some time ago I asked in the comments to some other post about a steel plate to use as a Teppan Yaki grill on my 11 inch induction burner, I guess the Wagner griddle plate will be perfect for that, can´t wait…

But now finally to my 2 cts of potentially useful input:
Wouldn´t castor oil be ideal for seasoning?
The hydroxy groups of its main component the ricinoleic acid make it stick very well to metals. (That is why it was used in the development of early oils for high performance engines – think Castrol).
Its added double bond will aid polymerisation once heated.
Anybody got experinece with this?
Otherwise I´ll just try it out. I can always burn it off if it don´t behave properly….

I finally got the skillet and the 11.5 inch griddle plate delivered by a friend coming over from the US (thanks, Tom). The polished surface of Wagner is really good. You cannot buy this in Europe.
I seasoned them with crestor oil at 200° 1h in the oven. It work like a charm.
The skillet was like non stick from the first use on. I love it. It is the best thing I ever had for steaks or back of lamb.
It gets really hot on my induction burner and when I put the meat in it is a true you to hear it scream. LOL.
1 min. on each side and then let it rest in the warm oven, fantastic!

The griddle plate fits perfectly on my 11 inch induction burner. It is my substitute for a Teppan Yaki grill. It also rocks when you jam 4000 Watts into it…..

I have had very little luck getting a good cast-iron preheat on an induction burner before their thermal sensors send them into protect mode. Admittedly, I haven’t crossed the $400 mark on a single burner hob, but of the 4 I’ve tried, they all seem to hate cast iron. Any tips or product recommendations will be appreciated, since it seems that others are making this combo work for them. Oh, and I have tried a towel between pan and glass, and that may help a little, but not much.

I re-conditioned my 6 qt. Lodge dutch oven tonight. Put it in the oven on the self-cleaning cycle, and sure enough the old surface completely burned off. I removed the ashes, rinsed the vessel and dried it thoroughly. Now all I needed to do was re-season it.

I had a can of White Cap Baking Release spray on the counter next to the stove, and a light went on in my head.

The spray application was easily controllable. I just “painted” the vessel (inside & out) with a light coat of the White Cap and chucked it into a 500 deg. F. oven, upside-down, with the bailing wire extended to provide more exposure.

I baked the vessel for one hour, shut off the heat, and let it cool down in the oven for another hour.

Result: the dutch oven has a thin, hard black coat of seasoning. It almost looks like Teflon.

I will repeat the process again but honestly it already looks better than the day I bought it – whether it stands up to regular use remains to be seen.

I’m curious to see if anyone can repeat my results, or find any faults with this process.

I’ve cooked a bit on a wood stove, which had a number of burner holes in different places on the cooktop, which itself was 1/3 over the firebox and 2/3 over the oven (hot gasses from the firebox traveled over the top of the oven, heating it from the side and top before exiting through the stovepipe). Pots could sit directly on the cooktop or over any one of the burner holes, which themselves could be all or partially uncovered. By varying pot placement and degree of burner opening, you could get a HUGE range of cooking temperatures without varying the size of the fire — which was also an option!

Nice tidbit: if you kept a small, slow fire burning throughout the day, a nice, even simmering heat was available at (you guessed it!) the back burner.

Thanks for this post! I used to have trouble with getting seasoning on cast iron to stay, baking the seasoning at the lodge-recommended 350F. Ever since switching to 500F seasoning on the grill everything’s been great.

Whenever I feel the coating on my Lodge six-quart is getting iffy I just pop a couple batches of popcorn in it. Use canola oil, wipe it out when I’m done and it’s good to go. Wife/kids love the popcorn, too!

Coming in way late, but I wouldn’t be surprised if the temp limits for enameled pans are about mismatched expansion between the metal and the enamel. I do know from experience that rapid temp changes will fracture enamel. (I had a le creuset pot that I used for cooking bulghur, which involves toasting the grain in oil and then adding water/stock. One day about a third of the bottom came up.)

I have always heard that you should NOT use metal utensils in a cast iron pan, to prevent damaging the seasoning. Are metal utensils really safe/beneficial to use? If so, that would make my life much easier, so I hope so!

Excellent point about the “high spots,” and that’s exactly why I give my cast pieces a firm exfoliation with a dough scraper after (particularly high-heat) use. It seems only to improve the release characteristics of a well-seasoned pan.

To the radio show caller looking for advice on a dutch oven, I can share some very good experience with – of all things – my “discount” Mario Batali 5 qt. enameled cast iron dutch oven. I bought it for about $80 (Amazon, on sale), when I couldn’t stomach the Le Crueset price. I’m thrilled with it. It is heavy, durable, heats evenly (I saute in it all the time), has small drip points inside the lid to encourage even condensation during cooking, and has generally been great. It also has a metal knob… I’ve baked bread and other dishes in this at up to 450 (IIRC), and the knob and finish have been fine.

Highly recommended. I know they’re sold in Crate & Barrel in addition to Amazon, but I’m guessing Amazon will win on shipping. The cost savings is amazing, but at least when I bought they didn’t have an oval 7 qt. option like the other brands.

I’m glad to see someone point out that iron is a poor conductor of heat. Just one thing though, there are no pores. Iron isn’t a porous material. It has a very UNEVEN surface at the microscopic level (like everything else), but this is not the same as porosity.

“dutch ovens (dutch meaning “fake”, not “from Holland”),”
I am curious if you could explain this statement, a quick Google search seems to show that ovens of this nature were being produced in Holland and great Britain in the 1700’s or earlier but that the naming may have resulted from the work of Abraham Darby and or the fact that this style of cast iron pot was also sold by Dutch traders.

Howdy N.walker,
Perhaps i was hasty in my acceptance of the explanations I have read. I no longer have access to OED online or I’d check them (even though they are often wrong on food terms). I found some of the same references you point to, as well as ones saying the pilgrims brought them from Holland (which, I think, is crap).

I read the Wiki entry on Dutch Ovens that has Abraham Darby visiting Holland in 1704, but further research seems to point out that he wasn’t researching iron in Holland, he was researching brass, and turned to iron later. He developed many of the processes that mad mass produced cast iron possible. I don’t have time to suss out the truth right now. Tell me what you find.

Here is a reference that points to both possibilities:

“Since c.1600, Dutch (adj.) has been a “pejorative label pinned by English speakers on almost anything they regard as inferior, irregular, or contrary to ‘normal’ (i.e., their own) practice” [Rawson]. E.g. Dutch treat (1887), Dutch uncle (1838), etc. — probably exceeded in such usage only by Indian and Irish — reflecting first British commercial and military rivalry and later heavy German immigration to U.S.

The Dutch themselves spoke English well enough to understand the unsavory connotations of the label and in 1934 Dutch officials were ordered by their government to stop using the term Dutch. Instead, they were to rewrite their sentences so as to employ the official The Netherlands. [Rawson]

Dutch oven is from 1769; OED lists it among the words describing things from Holland, but perhaps it is here used in the slighting sense. Dutch elm disease (1927) so called because it was first discovered in Holland (caused by fungus Ceratocystis ulmi).” from http://www.etymonline.com/index.php?term=Dutch

The OED online sez: ” b. Often distinguishing a particular sort of article, originally made in or imported from Holland: e.g. [many, many examples omitted] Dutch oven (see OVEN n. 2a); also slang, a person’s mouth”.

Dave, a cursory Google search didn’t give me anything but I think I remember Alton Brown talking about NOT deep frying in CI. I just got my 8 qt Lodge dutch oven and have started deep frying in it. Is my mind just mush or is there some truth to this?

Also: DAVE ARNOLD USING FAHRENHEIT? SOMEBODY CALL CHICKEN LITTLE. (Assume it was just for the magazine piece.)

Howdy Rusty,
I do, indeed, use Fahrenheit for deep frying. Dunno why. I do all my normal and low-temp in C. I do all my cocktail work in C. I do the weather, baking, and frying in F. Weird, right? I don’t see why cast iron would be bad for frying. Some metal ions, particularly copper, cause rapid oil breakdown. If there is some residual copper (or other reactive ion) in CI they might cause a problem if you planned on re-using the oil. Maybe he is worried about some reaction due to oil contact with the seasoning layer? I don’t know about any of that, but I do know people have been frying in CI for a long time.

You say unsaturated oils are best but is there a reason to prefer monounsaturated or polyunsaturated, or it just doesn’t matter much? E.g. is safflower better than sunflower or vice-versa? http://en.wikipedia.org/wiki/File:Fatchart.svg

I have a large Lodge frying pan which I’ve tried to season a few times: I’ve used it for campfire cooking several times, and the latest time I tried to season it with goose fat (I thought the old-timers considered it the best possible frying fat, and we tried goose a few months ago so I rendered some fat from that) over my charcoal grill. But it still seems to me that everything sticks to it; I can’t cook an omelette without having brown stuff all over the bottom, then have to soak it to get that off. Same thing with potatoes. Just can’t figure out what I’m missing. Maybe I just tend to cook everything at a higher temperature than it needs to be. Sounds like you’re suggesting it would be best to strip it, sand it to expose some of the internal roughness and then re-season it, rather than to just keep adding layers to what I’ve got? Anyway we are trying to be vegetarian a lot of the time, so I’m not going to be cooking a lot of bacon etc. which would probably be better for the pan. I’d like to use it mostly for the typical breakfast stuff anyway, if I could get it to the point of being truly non-stick. Until then we keep using the teflon pans, but I’d like to get away from it with the rumors about teflon being carcinogenic.

Sorry for the delay,
My guess is that oils that work best are ones that oxidize easily and polymerize (drying oils), but I think that anything will work at the temperatures involved in seasoning. It takes several seasonings before you get any non stick benefits. What you want to guard against is goopy drops. The surface of the pan shouldn’t feel tacky at all or be brown. It should be black and hard.

Hello Harry, there is an interesting train of discussion among some friends of mine whether there is any actual bluing of the metal taking place in normal seasoning (generation of Magnetite). I don’t know if has been resolved yet.

The silver could be an old nickle or chrome plating. Sometimes the old cast iron pans were plated. Over the years the plating wears off but occasionally it will remain on the handle. Sometimes an old nickle or chrome plated pan will show up on eBay.

thank you very much ! can u used cast iron for heat forced blood circulation for muscle damage therapy … heat a cast iron plate and sleep on it after covering it with blankets to heat ur muscle overnight ! i think this is done with stones …

Just ground one of my 12″ Lodge pans (fabric-backed abrasive disk, on a rubber pad chucked in my electric drill) to remove the factory-applied pre-seasoning. I told my daughter to wash the pan before I re-seasoned it, and she ran it through the dishwasher. An odd thing happened. First, the pan acquired a thin layer of rust (scarcely surprising, and easily removed), but there also appeared what looked like a network of dark lines (almost like fine surface cracks), mostly parallel to each other (about 1/8″ apart) and roughly perpendicular to the handle, kind of like a pen-and-ink drawing of a rough masonry wall. I went ahead and seasoned the pan, and the lines are no longer visible.

Question: is this some aspect of the grain of the metal? I suppose that it may have been there previously, and just was (a) obscured by the old pre-seasoning and (b) not visible in the freshly-ground surface without any oxidation to reveal it. I can’t imagine that the dishwasher could have caused it!

Infinitely. Lodge’s pre-seasoning is rough and pitted, and the new surface is nice and smooth (although I did run out of patience, and stopped grinding before ALL the pits were removed). Canola oil and 500 degree oven (occasionally removing from oven to wipe on another thin layer of oil); worked very nicely. I had done the same with a Matfer Bourgeat saute pan and had the entire seasoning layer peel off; apparently I hadn’t fully removed the coating they put on the metal to keep it looking nice in shipment. A firm scrubbing with fine sandpaper, and it re-seasoned beautifully.

We have a double propane Krampouz crepe griddle and are in need of help to fix it….uneven heat and changes in flame being the problem. Eurodib has not been too helpful. Do you know of anyone who might be able to help….in whatever way possible? I am loosing business by the week! Thanks!! Susie

Hi Susie,
I have a Krampouz, but its heat is extremely even. Are you running the crepe maker with a propane orifice or are you trying to run a natural gas orifice krampouz on propane? Mine came from the factory (I bought it in France) with a natural gas orifice.

The Krampouz can also have problems if its heat load changes a lot. It is designed to bang out crepes (which is a heavy heat load becasue it is a big wet cold thing spread over a large surface area) one after the other without pausing. It makes sense that the first couple of crepes you make won’t come out perfectly while it stabilizes. Also, you’ll need to set the unit lower if you are only making a couple of crepes per hour, and higher if you are in continuous production. I will often cool it if it gets too hot with a wet rag.

Hi Dave: We just bought a Samsung Induction Range. I need to buy new cookware and am confused as to what I need even though I’ve done my homework online. I have an old 40-year iron skillet but am confused that the flour example of uneven heat is not what I need! What do you suggest? We are now mostly vegan (about 95%) and will not be frying; probably water sauteeing.

Howdy Sylvia,
If you have water in the bottom of the pan, evenness of heat won’t be too much of a problem till you run dry –when you’ll get localized scorching. With the cast iron on an induction unit, if you need more even heat you will have to add it slowly. Incidentally, if you have some old all-aluminum pots or pans and want to use them on your induction you can put them inside the cast iron (if it is big enough) and use the cast iron like a flat-top.

Thanks AJ and Sam, mine are le chasseur, and the nob is metal. They still say to keep the temperature moderate. I tend to agree that any good cookware should be able to handle higher temperatures too, and I can’t think of any reason why these couldn’t. I think since un-enamelled CI can go so high it must be something to do with the coating – or maybe its just an old wive’s tale?! Who knows? I’m going to do some more research and will post anything I find out.